Washington: In a new study, a researcher has tried to find what makes infants chuckle. Last time around, the experiment involved a toy clown attached to a piece of string, which scientists held in front of their tiny, unwitting human guinea pigs to see if and when they would laugh.

Fortunately Dr Caspar Addyman's experiment, which he launched in August this year, is a little more complex. "Smiling and laughing are indices of our understanding of the world. Adults laugh at something when they find it surprising or unusual; it is exactly the same for babies," the Independent quoted him as saying.

"Finding out what makes infants laugh teaches us more generally about how humans understand and respond to the world around them, and also the ways in which that can change," he said. His gleeful subjects, who are all aged between two months and two years, are helping him to hunt for information that could eventually be used to determine how different developmental groups respond to stimuli at different stages and might ultimately lead to interventions.

It is all smiles in Babylab HQ, at the Centre for Brain and Cognitive Development, Birkbeck, University of London. For the past two months, Dr Addyman has been observing the humours of babies. For him, the measurement of laughter is just another tool in our understanding of how babies learn.

Technologies like eye tracking - infrared lights attached to a computer which capture corneal reflections, recording exactly what a baby is looking at - and electroencephalography, which measures brain activity, showing when and approximately where in the brain information is processed, have meant huge advances in studies in brain development over the past two decades.

But there is one thing, Dr Addyman says, that you still cannot do in a lab - make a baby laugh on demand. Accordingly he has launched his study online, allowing parents to log their children's laughter and Dr Addyman to record results as they are played out in real life. As well as being able to access participants from outside central London, it also saves the lab, which relies on grants, a fair bit of cash.

Leslie Tucker, the centre co-ordinator, explains that Dr Addyman's "crowdsourcing baby research" represents the future of information gathering. "Although we haven't analysed the data in detail yet we can definitely see a few trends," Tucker said. "So far, we've found that daddy seems to be the funniest person, with mummy a close second. Peekaboo is the funniest game but tickling, funny voices and blowing raspberries are all sure-fire hits," she said.

For the record, Dr Addyman adds, we can dispel the myth that your baby's earliest smiles are just trapped wind. "A lot of first smiles and laughs are happening in the first four months of life, far earlier than traditional theories claimed. Babies' first-ever smiles are often seen as young as one to three months old, with social smiles [that's smiling at a person] starting shortly afterwards, between two and four months, and laughter following on soon, at three to six months," he added.